[leish-l] leishmaniasis outside endemic area

[Richard Ashford]

Dear all,

Re: imported human VL

Over quite a number of years I have attempted to 'collect' cases of human 
VL imported into non-endemic areas. My question has been whether the 
age-distribution of human cases is the same (for L. d. infantum) as it is 
in enedmic/enzootic areas. There are too few cases to be conclusive, and 
the age structure of the travelling population is different from that of 
the indigenous populations, so both numerators and denominators are 
questionable. Overall, however, there does seem to be a preponderance of 
infants among (non-HIV) cases imported into non-endemic areas which, if 
substantiated, would support the idea that the rarity of cases in adults 
has less to do with acquired specific immunity, than some aspect of the 
normal development of innate immunity.

I suppose that L. d. infantum infects H. sapiens adults only with great 
difficulty, but is able to infect at least a small proportion of infants.

A large scale skin-test study in an endemic area might show that people of 
all ages are equally exposed, becoming skin test positive as a result, but 
that only a very small proportion of infants, and selected adults get sick.

Does this make sense? Does anyone know why L. d. infantum specialises in 
infants?Can anyone add some data to my hand-waving generalisation? I wonder 
if a sufficiently large skin test study, with detailed age breakdown has 
been done?

By the way, though L. d. donovani and l. d. infantum are very closely 
related (there is probably no combination of taxonomic character-states 
that can reliably separate them, that also coincides with their biology), 
their behaviour in humans is very different, so it is wrong to extrapolate 
results of, for example, nutritional-state-susceptibility studies, from one 
form to the other.

Happy new year,

Dick Ashford



--On 11 January 2003 12:45 +0100 nicleger <nicleger at wanadoo.fr> wrote:

>
> Des vecteurs prouvés ou suspectés ont été à plusieurs reprise signalés en
> dehors des zones d'endémie leishmanienne. Récemment l'un de mes élèves en
> a même capturé à Reims (été 2002) ! Un de nos collègues allemand (
> Torston NAUCKE) a effectué une enquête autour d'un cas apparemment
> autochtone de leishmaniose canine . Il l'a ensuite étendue à d'autres
> régions d'Allemagne et également aux Ardennes belges et françaises où il
> a signalé la présence de P.mascittii et un peu plus tard de
> P.perniciosus. Demandez lui ses tirés à part.  Entomologiquement vôtre.
> N.LEGER.